In the case where a storage area storing files is backed up a plurality of times at time intervals, the storage capacity of a backup destination becomes huge when all files in the storage area are backed up each time. Therefore, a differential backup is performed in which only files that are updated since the previous backup time is backed up, thereby saving the storage capacity of the backup destination.
The following backup system has been proposed for data backup. An information processing device included in the backup system records information indicating a backup time in file management information included in a file stored in a storage. The information processing device compares the file management information at a predetermined backup time to the file management information at another backup time, and acquires and records the difference information obtained through the comparison.
The following storage device has also been proposed. The storage device synthesizes data stored in an operation volume with difference data stored in a difference volume on the basis of mapping information for managing a relationship between data regarding the operation volume and data regarding the difference volume storing the difference data between a snapshot and the operation volume, and transmits the synthesized data to a backup device.
Related technologies are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2009-163334 and Japanese Laid-Open Patent Publication No. 2005-284609.